The present invention relates to novel chemical-resistant sealing and lubricating compositions. More particularly, the present invention relates to a grease composition which is chemically-resistant and is useful for lubricating and/or sealing mechanical seals, valves, flanges and the like.
Although there are many grease compositions known in the art, surprisingly few of them are chemically resistant.
One grease composition which is said to be chemically-resistant is taught by U.S. Pat. No. 2,563,606. In accordance with this patent a grease is prepared by replacing the water in a hydrogel such as silica, alumina, stannia, etc., with a liquid which has lubricating properties but which is suitably resistant to solution or reaction with the chemicals which it is expected to contact. Example 1 of this patent shows the preparation of a silica by the reaction of sodium silicate with sulfuric acid; and use of the silica product to form a grease comprising 6.4% silica and 93.6% glycerine. An essential step in the process is the milling of the silica in the presence of the lubricating liquid.
Although the liquid component of the grease taught by the patent may be resistant to specific chemicals, the overall quality of the resulting grease may be less than desirable.
In addition to pure chemical resistance, considerations must be given to hygroscopicity, thixothropy and weather-resistance. Thus, for example, the grease should be thixotropic so that it will flow well then being pumped through a grease fitting, but then have sufficient body so as not to flow out of the mechanism to which it has been applied. The grease should also be sufficiently water-resistant so that it will not be washed out of, for example, a valve or a pair of flanges when installed outside and exposed to rainfall.
U.S. Pat. No. 3,107,219 teaches an "energizable" grease composition comprising a base lubricant which is a polyhydric alchohol or derivative thereof, a thickener which is at least 2/3 potash soap, and a gas entraining agent.
It would be expected that this grease would be unsuitable for some chemical operations because the presence of the potassium ion as well as the gas entraining agents could lead to harmful effects.
It is therefore apparent that a need exists for a new grease composition that is chemically-resistant, has good grease properties, and contains no harmful ionic-salts or surfactant components.